finding 26.2 : key-message-26-2

Alaska residents, communities, and their infrastructure continue to be affected by permafrost thaw, coastal and river erosion, increasing wildfire, and glacier melt. These changes are expected to continue into the future with increasing temperatures, which would directly impact how and where many Alaskans will live (very likely, high confidence).

The Alaska regional chapter was developed through public input via workshops and teleconferences and review of relevant literature, primarily post 2012. Formal and informal technical discussions and narrative development were conducted by the chapter lead and contributing authors via email exchanges, teleconferences, webinars, in-person meetings, and public meetings. The authors considered inputs and comments submitted by the public, the National Academies of Sciences, Engineering, and Medicine, and federal agencies. The author team also engaged in targeted consultations during multiple exchanges with contributing authors, who provided additional expertise on subsets of the Traceable Account associated with each Key Message.

The shoreline along Alaska's northern coast has eroded at some of the fastest rates in the Nation, putting local communities, oil fields, and coastal habitat at risk.cf15559b-f1e8-4022-945b-45ab149dc1a8 Unlike the contiguous United States, Alaska is subject to glacial and periglacial processes that make permafrost and sea ice key controlling factors of coastal erosion and flooding. Thermal degradation of permafrost leads to enhanced rates of erosion along permafrost-rich coastal shorelinescf15559b-f1e8-4022-945b-45ab149dc1a8 and subsidence of already low-lying regions. Longer sea ice-free seasons, higher ground temperatures, and relative sea level rise are expected to exacerbate flooding and accelerate erosion in many regions, leading to the loss of more shoreline in the future.cf15559b-f1e8-4022-945b-45ab149dc1a8

While erosion and changed river courses are a normal part of landscape evolution, lateral river erosion rates are likely to change over time, but the direction and magnitude of these changes are poorly understood. Major river erosion events are typically tied to high hydrological flows or the melting of permafrost along river and stream banks. Statewide, evidence for changes in maximum gauged streamflows is mixed, with a majority of locations having no significant trend.41ed988f-4fa6-476d-90c9-ef9e3e8d1806 There is significance for seasonal changes in the timing of peak flows in interior Alaska, though increases in the absolute magnitude are not well evident in existing data.5e61fa98-c1ff-42e6-aa82-10dad90342d9 Riverine erosion is a serious problem for a significant number of communities.49a37e8f-eef6-4ee6-9705-fac54c48df30 Significant resources have been expended to slow erosion at some communities, often through the construction of berms and bank stabilization projects. These projects have a mixed record of success and nearly always require ongoing maintenance.

Some events such as wildfires and coastal storms are dependent on regional and local current weather conditions, and the exact landscape or ecosystem response can be highly variable. Future effects are also dependent on quick response actions and adaptation measures.

Assessment of confidence based on evidence:

There is high confidence that wildfire in Alaska will continue but medium confidence as to its ultimate effect on vegetation and permafrost, which is often dependent on fire fields available (e.g., older forests or new growth shrublands), the fire intensity, and the return rate. There is high confidence that the north coast of Alaska is eroding at high rates. It is likely that coastal erosion is accelerating in response to climate change but medium to low confidence as to the location and rate because of limited studies and datasets documenting this. There is high confidence that river erosion will continue but medium confidence as to when, where, and to what extent this will occur across Alaska because of differences in local climatic and geographic qualities of the area in question. There is high confidence and it is likely that the glaciers in Alaska will continue to diminish, especially those that are tidewater glaciers.